The present invention relates to microfluidic devices. The integration of laboratory operations on a microfluidic device has numerous applications in medical diagnostics and biological science. Research into microfluidic devices, which perform various functions for biochemical reactions using biochemical fluids, such as blood, urine, saliva and sputum, for example, and detect the results thereof, has been actively pursued. Microfluidic devices may be of a chip type such as a lab-on-a-chip or of disk type such as a lab-on-a-disk. The lab-on-a-chip and lab-on-a-disk have received much attention in chemical and biotechnology fields since such devices may increase reaction rates, be automated, be made portable, and use a small amount of reagent. A microfluidic device typically includes a microchannel, through which a fluid flows, and a microvalve, which controls the flow of fluid in the microchannel. In a microfluidic device, the microvalve or microvalves control the transfer, mixing, accurate metering, biochemical reaction, isolation and detection of a sample in the microfluidic device of a chip type such as a lab-on-a-chip.
A variety of liquid handling operations can be performed using microfluidics technology, thus allowing complex laboratory assays to be automated on a compact chip. Integrated microfluidics is a technology that allows valves and pumps to be built right on the microfluidics chip, thus allowing complex liquid handling and a high degree of multiplexing. In order to execute the required liquid handling operations, the valves and pumps on the chip must be activated at the proper time. Typically, this is achieved by computer controlled pneumatic actuators that sit outside of the chip itself and are connected to the chip through a network of tubing. While this has worked well in engineering laboratories, the considerable amount of off-chip machinery is too cumbersome and complex for general use. The need for off-chip controls introduces significant disadvantages in terms of size, cost, ease of use, and reliability. The implementation of digital logic circuits out of microfluidic valves and channels could potentially enable fully self-contained systems that are controlled by onboard circuitry, thus eliminating the need for off-chip controls.